In the prior art, in the creation of semiconductor devices, a photoresist layer is applied to create a pattern. The photolithography process using photoresist is described in "Microchip Fabrication" by Peter Van Zant and published by McGraw-Hill, Third Edition 1997, pp 192 -197, and 273-277. A photoresist layer is spun onto a surface of a substrate and dried. A mask or reticle is placed over the photoresist layer. The photoresist layer and mask are exposed to light, which causes masked portion of the photoresist layer to remain and unmasked portions of the photoresist layer to develop soluble. The soluble parts of the photoresist layer are removed with a solvent, leaving a photoresist layer pattern. The photoresist layer pattern is used as a mask for ion bombardment or plasma etching. Ion bombardment and plasma etching of the photoresist causes a hardening of the surface of the photoresist. Chemical stripping, used in the prior art, is not able to remove all of the hardened surface of the photoresist layer. Scrubbers such as a brush and water jet, also used in the prior art, are also not able to remove the hardened surface of the photoresist layer. Plasma stripping, which is also used in the prior art, is able to remove the hardened surface of the photoresist layer, but requires a charge which may damage the semiconductor devices. The incomplete removal of the hardened surface of the photoresist layer causes the incomplete removal of the remainder of the photoresist layer, thus leaving photoresist residue such as particles of heavy metals, which may diminish the performance of transistors by causing source, drain, and gate edges, in addition to causing open circuits or shorts.
It would be advantageous to have a method of removing the photoresist layer more completely without damaging the underlying semiconductor device.